Pink colored metal alloy having low gold content

ABSTRACT

Pink colored metal alloys have a low gold content. The pink colored metal alloys of the present disclosure display a high level of tarnish resistance during extended use and wear, and have the appearance and properties comparable 10 karat (or above) gold alloys, which have a significantly higher gold content.

CROSS-REFERENCE TO RELATED APPLICATION

This nonprovisional application claims the benefit of U.S. Provisional Application No. 61/563,095 filed Nov. 23, 2011. The disclosure of the prior application is hereby incorporated by reference in its entirety.

BACKGROUND

This disclosure relates to pink colored metal alloys comprising gold, copper, silver, zinc and optionally other elements, in amounts suitable to create a pink colored metal alloy (having a low gold content) with improved properties, such as, for example, tarnish resistance.

10 karat to 18 karat gold products (e.g., alloys) are commercially available in many standard colors, including yellow, white, green, red and rose. For such alloys, which have a high gold content (i.e., higher than 41.67%), the amount of gold in a particular alloy is generally measured in terms of “karats.” For example, pure gold (i.e., 100% gold) is referred to as 24 karat gold. Thus, the number of “karats” in the gold divided by 24 yields the percentage of gold in the alloy. For example, an alloy of gold that has 50% gold would be referred to as a 12 karat gold. 18 karat gold would be an alloy that has 75% gold, etc. However, in the United States, such nomenclature (referring to “karats”) is generally limited to alloys having a gold content higher than 41.67% (i.e., 10 karats), and will not be used in the present application to describe alloys having a gold content lower than 33%. See 16 C.F.R. §23.4.

Commercially available “karat” gold alloys (i.e., alloys having a gold content higher than 41.67%) may include very small amounts of a variety of elements that perhaps create a characteristic (reversible hardness, a spring effect, or deoxidant, improved flow and form filling during investment casting etc.) that is generally applicable only to a very small segment of jewelry manufacturing. While such alloys are suitable for their intended purpose, there is a need to generate a more versatile general purpose pink colored metal alloy that contains less gold, but still has an appearance and properties comparable to the higher “karat” alloys.

By reducing the amount of gold in the alloy, the cost of the material decreases (and thus reduces manufacturing costs). At the same time, as the amount of gold decreases, the resulting alloy is less likely to have all of the properties associated with gold. For example, for alloys having less gold, it is has been found that these materials are more likely to tarnish and can even cause a person's skin to discolor if used in jewelry. Clearly, such properties are undesirable and would inhibit a jeweler's ability to sell such a product. Thus, a need also exists for less expensive pink colored metal alloys that have the appearance and properties comparable to the higher “karat” gold alloys.

The present disclosure addresses the above needs by providing pink colored metal alloys having a low gold content (less than 33%), which may be used in a number of applications. The pink metal alloy of the present disclosure has low gold content but still maintains important characteristics and properties comparable to known “karat” gold alloys (i.e., alloys in which the gold content is higher than 41.67%), e.g., high degree of luster and shine, tarnish and corrosion resistance, resistance to cracking, surface smoothness and for jewelry applications, very good wear and durability properties.

SUMMARY

According to some embodiments, a pink colored metal alloy comprises, by weight percent with respect to the total weight of the alloy: about 33.0% to about 20.0% Au; about 60.0% to about 45.0% Cu; about 14.8% to about 2.5% Ag; and 0% to about 5.0% Zn.

According to some embodiments, a pink colored metal alloy comprises: gold, copper, zinc and silver, wherein the gold is present in an amount of from about 33.0% to about 20.0% by weight percent with respect to the total weight of the alloy; and ratios of the percentage by weight, with respect to the weight content of gold, copper, zinc and silver only, of Cu:Ag and Cu:Zn are from about 15(Cu):1.0(Ag) to about 3.0(Cu):1.0(Ag) and from about 70(Cu):1.0(Zn) to about 15(Cu):1.0(Zn), respectively.

DETAILED DESCRIPTION OF EMBODIMENTS

The present disclosure relates to pink colored metal alloys having a low gold content. The pink colored metal alloys of the present disclosure display a high level of tarnish resistance (greater than that of sterling silver) during extended use and wear, and have the appearance and properties comparable to “karat” gold alloys, which have a higher gold content, such as 10 karat (and above), yet contain lower amounts of gold (by weight), for example, less than about 33% gold, such as in the range of from about 33% gold to about 20% gold, or in the range of from about 32% gold to about 25% gold, or in the range of from about 30.5% gold to about 27.5% gold.

In embodiments, the pink colored metal alloys of the present disclosure may be used to manufacture jewelry by investment casting. The present disclosure also relates to a cast object comprising the pink colored metal alloys defined herein.

The pink colored metal alloys of the present disclosure may also be formed into manufacturing stocks such as by casting grains, rolled goods such as sheet and wire. Known methods and processes for the casting, fabrication and finishing of jewelry are effective with the pink colored metal alloys of the present disclosure.

The pink colored metal alloys having a low gold content of the present disclosure may be practically utilized in the jewelry industry and/or can readily be cast, soldered or cold worked, such as forging and rolling. Such pink colored metal alloys of the present disclosure possess excellent metallurgic and physical properties and may be designed to include a moderate level of hardness to extend the resulting product's (such as jewelry) wear and polish life without adversely affecting malleability and ductility. The high level of malleability and ductility of the pink colored metal alloys of the present disclosure results in superior processibility during manufacturing, for example, during processes including forging and/or machine forming, and also allows the same (i.e., compositionally identical) alloy of the present disclosure to be made into various fowls of sheet and wire. The pink colored metal alloys described herein also display a level of fluidity that allows smooth, detailed castings. Additionally, products made from the pink colored metal alloys, whether cast or formed are easily joinable with solders. The pink colored metal alloys of the present disclosure possess the above properties and have excellent memory (ability to hold form) and annealability (a resoftening process using heat).

In embodiments, the pink colored metal alloy of the present disclosure may be prepared by preparing a master alloy made up of at least copper, zinc and silver. In such embodiments, the methods of the present disclosure comprise pre-forming the master alloy and then mixing a desired percentage of the master alloy with a desired percentage of gold to form the resulting gold alloy. In embodiments, the master alloy optionally comprises one or more other elements, such as silicon, germanium, iridium, cobalt, boron and ruthenium. In at least some embodiments, palladium is excluded from the master alloy and pink colored metal alloy.

The percentage of the master alloy may be represented by the variable “Q” and the percentage of the gold may be represented by the variable “Y.” Specifically, Y% gold may be mixed with Q% master alloy to form the pink colored metal alloy. The percentages of gold and master alloy must add up to 100% (i.e., Q+Y=100). In such embodiments, Y may be less than about 33, such as in the range of from about 33 to about 20, or in the range of from about 32 to about 25, or in the range of from about 30 to about 28, where Q makes up the remaining balance.

Known metallurgy methods may be used to prepare the pink colored metal alloy of the present disclosure. Exemplary methods for preparing a pink colored metal alloy of the present disclosure may include mixing gold with a master alloy to obtain the pink colored metal alloy, wherein the composition is based on the use of pure metals (99.9% or better) and the pink colored metal alloy is made in a standard crucible melt (e.g., gas or electric) and may be fluxed with known industry flux formulas and techniques.

In embodiments, when the melt has evenly mixed, in its molten state, it may be cast into articles of jewelry by the use of, for example, either vacuum casting equipment or centrifugal equipment. Usual cooling times and quenching techniques may be used to recover castings. A prepared melt in its molten stage, homogeneously mixed, may also be poured into ingots, bars, or grain, later to be used as a stock to create rolled sheet, tubing, dimensional wires, round wire, solders and castings for the manufacture of jewelry.

In embodiments, a sample with a particular mix of elements in amounts suitable to make the pink colored metal alloy of the present disclosure may be melted in commercially available continuous casting machines, and processed by known methods into various forms (and dimensions) including for example, wire, sheets, and tubing.

In embodiments, the methods of the present disclosure may comprise preparing a pink colored metal alloy by mixing gold with the desired elements by known methodology, without first forming the master alloy. For example, the pink colored metal alloys of the present disclosure may be manufactured by standard procedures used in the manufacture of precious metal alloys. In embodiments, the pink colored metal alloys of the present disclosure, which may have a melting range of between about 1300° F. and about 1650° F., may be prepared by weighing out the appropriate proportions of the elements, combining them in a suitable container, such as a crucible, and applying a heat sufficient to melt the materials. Additionally, for example, the melt may be stirred with a suitable stirring device before pouring into grain form to assure uniform alloying.

In embodiments, the raw materials may be directly made into a desired form (e.g., a sheet, wire, tube, etc., which optionally may be further processed) without the need for obtaining a granule form of the pink colored metal alloy. Such embodiments may employ commercially available casting equipment capable of sufficiently stirring the liquid alloy.

In embodiments, the present disclosure may further relate to a method for manufacturing pink colored metal alloys as defined above, which includes casting the constituent elements of the alloy, either in the pure state or in the alloy state, preferably under an inert atmosphere.

A key factor in the formulation of the pink color and improved properties of the metal alloy of the present disclosure is the percentage relationship by weight (i.e., weight relationship between pure (99.9% or better) gold, copper, zinc and silver.

In embodiments, various ranges may be used for each of the component elements in order to obtain a pink colored metal alloy. For example, the following weight percentage ranges may be used: less than about 33% Au, such as in the range of from about 33% to about 20% Au, or from about 32% to about 25% Au, or from about 30.5% to about 27.5% Au; in the range of from about 60% to about 45% Cu, such as from about 58% to about 52% Cu, or from about 56.0 to about 54.0% Cu, or from about 55.5% to about 54.5% Cu; from 0% up to about 5% Zn, such as in the range of from about 0.5% to about 5% Zn, or from about 0.6% to about 2.5% Zn, or from about 0.8% to about 1.2% Zn; in the range of from about 14.8% to about 2.5% Ag, such as from about 14.0 to about 8.0% Ag, or from about 12.8 to about 10.8% Ag, or from about 12.3% to about 11.3% Ag; and optionally from about 0.001 to about 1% X, such as about 0.05 to about 0.8% X, or from about 0.1% to about 0.3% X, where X is one or more elements selected from the group consisting of silicon, germanium, cobalt, iridium, ruthenium, and boron (and mixtures thereof).

Any and/or all of the embodiments described herein may exclude palladium from the pink colored metal alloy.

In embodiments, the resulting pink colored metal alloy may be produced such that the ratio of the percentage by weight (with respect to the weight content of gold, copper, zinc and silver only) of Cu:Ag may be in the range of from about 15(Cu):1.0(Ag) to about 3.0(Cu):1.0(Ag), such as from about 5.2(Cu):1.0(Ag) to about 4(Cu):1.0(Ag), or from about 4.7(Cu):1.0(Ag) to about 4.6(Cu):1.0(Ag); the ratio of the percentage by weight of Cu:Zn may be in the range of from about 70(Cu):1.0(Zn) to about 15(Cu):1.0(Zn), such as from about 60(Cu):1.0(Zn) to about 50(Cu):1.0(Zn), or from about 54(Cu):1.0(Zn) to about 56(Cu):1.0(Zn); and the ratio of the percentage by weight of Ag:Zn may be in the range of from about 20(Ag):1.0(Zn) to 6(Ag):1.0(Zn), such as about 13(Ag):1.0(Zn) to 10(Ag):1.0(Zn), or 12.1(Ag):1.0(Zn) to 11.5(Ag):1.0(Zn). In such embodiments, the weight content of gold of the pink colored metal alloy may be less than about 33% gold, such as in the range of from about 33% gold to about 20% gold, or in the range of from about 32% gold to about 25% gold, or in the range of from about 30.5% gold to about 27.5% gold.

Depending upon the intended use of the alloy, the pink colored alloy containing gold and the weight percentage ratio of copper, zinc and silver described in the above paragraph may contain lesser amounts of one or more optional elements selected from the group consisting of silicon, germanium, cobalt, iridium, ruthenium, and boron. For example, in embodiments, silicon may be included as a deoxidizer in an amount up to about 0.3% by weight of the pink colored metal alloy, such as from about 0.01% by weight to about 0.25% by weight, or from about 0.05% by weight to about 0.15% by weight. In embodiments, either with or without the above amounts of silicon, germanium may be included in an amount up to about 0.3% by weight of the pink colored metal alloy, such as from about 0.01% by weight to about 0.25% by weight, or from about 0.05% by weight to about 0.15% by weight.

In specific embodiments, the resulting pink colored metal alloy may be produced such that the ratio of the percentage by weight (with respect to the weight content of gold, copper, zinc and silver only) of Cu:Ag:Zn may be in the range of from about 60.0(Cu):13.0(Ag):1.0(Zn) to about 50.0(Cu):10.6(Ag):1.0(Zn), such as from about 56.0(Cu):11.0(Ag):1.0(Zn) to about 54.0(Cu):10.8(Ag):1.0(Zn). In such embodiments, the weight content of gold of the pink colored metal alloy may be less than about 33% gold, such as in the range of from about 33% gold to about 20% gold, or in the range of from about 32% gold to about 25% gold, or in the range of from about 30.5% gold to about 27.5% gold. Such a pink colored alloy may also contain lesser amounts of one or more optional elements selected from the group consisting of silicon, germanium, cobalt, iridium, ruthenium, and boron. For example, in embodiments, silicon may be included as a deoxidizer in an amount up to about 0.3% by weight of the pink colored metal alloy, such as from about 0.01% by weight to about 0.25% by weight, or from about 0.05% by weight to about 0.15% by weight. In embodiments, either with or without the above amounts of silicon, germanium may be included in an amount up to about 0.3% by weight of the pink colored metal alloy, such as from about 0.01% by weight to about 0.25% by weight, or from about 0.05% by weight to about 0.15% by weight.

In addition to the above components, any and/or all of embodiments described herein may include one or more grain refiners. Such grain refiners may be added in any suitable amount that does not substantially change the color properties of the alloy. Accordingly, those skilled in the art would appreciate how to implement and use these grain refiners.

Those skilled in the art would understand how to mix the elements together to obtain any desired gold alloy within the scope of the present disclosure. The present disclosure gives various examples of the alloys described herein. Those skilled in the art will appreciate that there are a variety of different applications, besides in the jewelry industry, for the alloys described herein, including dental applications, aerospace applications, metallurgy applications, electronic devices, etc. Further, another application includes using the alloys disclosed herein as a powder coating. The alloys of the present disclosure may also be used as part of plating solutions or electrically deposited onto a substrate. A further application may use the alloys as part of bi-metals, clad materials, or layer materials (i.e., where the alloy is a foil on a sterling silver backing (e.g., bi-metals) or brass substrate (e.g., clad materials) such that the customer only sees the foil layer on the outside). Findings, wires and rods, and other accessories may be made using these alloys. The processes used (plating, making clad materials, making bi-metals, etc.) as well as the types of materials that can be made using these alloys involve standard techniques known in the gold/metallurgical industry.

EXAMPLES

A number of examples are set forth below and are illustrative of different compositions that may be utilized to prepare pink colored alloys of the present disclosure. All proportions are by weight unless otherwise indicated.

The pink alloys of Table 1 were produced by conventional methods known to in the art. The raw components for the alloys were used as obtained from their commercial sources, without further purification. Inclusion of palladium resulted in an alloy exhibiting a less pleasing pink color and afforded no advantages in terms of properties over the exemplary pink colored metal alloys (Examples 1 and 2).

TABLE 1 Compositions of the alloys expressed as % by weight of the components. Au Ag Cu Zn Pd Si Ge (wt (wt (wt (wt (wt (wt (wt %) %) %) %) %) %) %) Comparative 20.00 39.89 38.46 0.50 0.75 0.20 0.20 Example 1 Example 1 32.00 11.80 55.00 1.00 None 0.10 0.10 Comparative 30.00 11.80 55.00 1.00 2.00 0.10 0.10 Example 2 Example 2 32.00 11.80 55.05 1.00 None 0.10 0.05

Decreasing the germanium content by 50% makes it easier to granulate. The alloy of Example 2 could easily be both investment cast and rolled/drawn into sheet, tube and wire product.

The grain was produced on an Indutherm GU1000 graining unit (Hoover & Strong, Inc.).

Tarnish resistance was assessed by a sulfur fume test in which ½ teaspoon of liver of sulfur was mixed with 350 milliliters of water (to form a “tarnish test mixture”) and placed in a sealable desiccator, which was 6 inches in diameter. The alloy of Example 2, prepared above, was tested relative to sterling silver and a commercially available 10 karat red gold (Hoover & Strong, Inc.). The samples to be tested were suspended approximately 1 inch above the tarnish test mixture and the desiccator was sealed. The test samples were exposed to the resulting sulfur fume environment for predetermined intervals. The tested samples were visually examined at 30 minutes, 60 minutes and 120 minutes for signs of discoloration. After 30 minutes, there were signs of discoloration on the sterling silver sample but not on the other two tested samples. After 60 minutes there were signs of discoloration on the pink alloy but not on the 10 karat red alloy. After 120 minutes there were signs of discoloration on all three samples.

It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. Unless specifically recited in a claim, steps or components of claims should not be implied or imported from the specification or any other claims as to any particular order, number, position, size, shape, angle, color, or material. 

What is claimed is:
 1. A pink colored metal alloy comprising, by weight percent with respect to the total weight of the alloy: about 33.0% to about 20.0% Au; about 60.0% to about 45.0% Cu; about 14.8% to about 2.5% Ag; and 0% to about 5.0% Zn.
 2. The alloy of claim 1, further comprising from about 0.001 to about 1% X, wherein X is one or more elements selected from the group consisting of silicon, germanium, cobalt, iridium, ruthenium, boron, and mixtures thereof.
 3. The alloy of claim 2, wherein X is silicon and germanium.
 4. The alloy of claim 3, wherein the weight percent of X from about 0.1% to about 0.3%.
 5. The alloy of claim 2, wherein X is silicon.
 6. The alloy of claim 2, wherein X is germanium.
 7. The alloy of claim 1, wherein the weight percent of the Au is from about 32% to about 25%.
 8. The alloy of claim 1, wherein the weight percent of the Cu is from about 56.0% to about 54.0%.
 9. The alloy of claim 1, wherein the weight percent of the Ag is from about 12.8% to about 10.8%.
 10. The alloy of claim 1, wherein the weight percent of the Zn is from about 0.8% to about 1.2%.
 11. A pink colored metal alloy comprising: gold, copper, zinc and silver, wherein the gold is present in an amount of from about 33.0% to about 20.0% by weight percent with respect to the total weight of the alloy; and ratios of the percentage by weight, with respect to the weight content of gold, copper, zinc and silver only, of copper:silver and copper:zinc are from about 15.0(Cu):1.0(Ag) to about 3.0(Cu):1.0(Ag) and from about 70(Cu):1.0(Zn) to about 15(Cu):1.0(Zn), respectively.
 12. The alloy of claim 11, further comprising from about 0.001 to about 1% X by weight percent with respect to the total weight of the alloy, wherein X is one or more elements selected from the group consisting of silicon, germanium, cobalt, iridium, ruthenium, boron, and mixtures thereof.
 13. The alloy of claim 12, wherein X is silicon and germanium.
 14. The alloy of claim 13, wherein the weight percent of X from about 0.1% to about 0.2%.
 15. The alloy of claim 12, wherein X is silicon.
 16. The alloy of claim 12, wherein X is germanium.
 17. The alloy of claim 11, wherein the weight percent of the gold is from about 32% to about 25%.
 18. The alloy of claim 11, wherein the weight percent of the copper is from about 56.0% to about 54.0%.
 19. The alloy of claim 11, wherein the weight percent of the silver is from about 12.8% to about 10.8%.
 20. The alloy of claim 11, wherein the weight percent of the zinc is from about 0.8% to about 1.2%. 